The Online Invoicing National Tax and Customs Hungary is a free mobile application for Android that enables users to issue invoices, modify invoices, submit invoice data in real-time, manage customers and products, query statistics, manage invoice pads, and access news published in the Online Invoice System. Created by the National Tax and Customs Administration of Hungary (NTCA), the app offers a portable format for Online Invoice System and Online Invoicing Program. To use the app, the user must be registered for the Online Invoice System and have an active internet connection, and the Android version must be 7.0 or higher. The app also allows users to enter via a QR code identification or primary and secondary user ID, and change the language to English or German within the Settings menu.